Biodiesel production

ABSTRACT

A reactor includes a shell having an input port configured to receive a reaction mixture and an output port configured to discharge a reaction product and a plug within the shell, the sintered plug having a first catalyst configured to transform the reaction mixture into the reaction product, the plug having pores of at least  0.01  micrometers (μm) diameter. A conduit includes a first and second lumen, the first lumen configured to carry a first fluid in a first direction and the second lumen configured to carry a second fluid in a second direction, the first lumen helically twisted relative to the second lumen, and the first lumen configured to conductively transfer thermal energy to the second lumen. A system includes a reactor with a sintered plug and a heat exchanger including a first and a second lumen helically intertwined about an axis.

CLAIM OF PRIORITY

This application claims the benefit of priority under 35 U.S.C. §119(e) of Mowry, U.S. Provisional Patent Application Ser. No. 61/611,719, entitled “BIODIESEL PRODUCTION”, filed on Mar. 16, 2012, which is herein incorporated by reference in its entirety.

BACKGROUND

Biodiesel can be produced by reacting a lipid (e.g., vegetable oil or animal fat) with an alcohol. Production can include synthesizing biodiesel via transesterification or alcoholysis. Biodiesel syntheses via transesterification or alcoholysis proceeds relatively slowly, or not at all. Therefore, biodiesel production facilities commonly use a relatively strong acid or a relatively strong base to catalyze the reaction. However, even catalyzed, typical biodiesel synthesis can take up to eight hours for complete conversion. As such, biodiesel is typically produced via a batch process. Due to the batch process design and the demand of biodiesel, biodiesel production facilities typically involve a large foot print for the production equipment.

Typical biodiesel batch processes are sensitive to free fatty acid (FFA) concentration and water concentration in the lipid. Consequently, preprocessing of the lipid to reduce FFA concentrations is typically done prior to commencing with any biodiesel production. Waste (e.g., soaps and glycerides, among others) can be washed out of the biodiesel product with water, producing contaminated waste water. In order to profitably produce biodiesel, typical biodiesel production facilities involve a relatively large footprint, as well as a relatively large start-up cost.

OVERVIEW

An example of the present disclosure includes a system with a heat exchanger and a reactor. The heat exchanger can conserve thermal energy by extracting otherwise discarded thermal energy from a reaction product stream. The reactor can synthesize biodiesel at supercritical reaction conditions, as described herein.

Biodiesel can serve as an alternative to non-renewable resources such as diesel. For example, biodiesel can act as a fuel for diesel vehicles in its pure form or as a diesel additive to reduce levels of particulates, carbon monoxide, or hydrocarbons from diesel-powered vehicles. In addition, homogenized biodiesel can serve as a jet propellant (e.g., JP-8) substitute. By providing an alternative to traditional fossil fuels, biodiesel can, for example: provide energy security, result in reduced greenhouse gas emissions compared to fossil fuels, be carbon neutral, and have a lower market price than fossil fuels.

In an example, a reaction mixture, including a lipid with an excess of alcohol, can be transformed into a biodiesel with excess alcohol. Excess alcohol can drive the reaction to completion (e.g., conversion of lipid to biodiesel). Excess alcohol from the reaction can be separated via a separator unit operation and recycled back into the process.

In an embodiment, the system can produce biodiesel via a supercritical transesterification and esterification process, as described herein. Benefits of such an embodiment, include, but are not limited to, higher lipid conversion to biodiesel than typical catalyzed biodiesel processes and faster reaction times than traditional catalyzed biodiesel systems. Due to the faster reaction times, in part, an embodiment of the present disclosure can include a continuous process for biodiesel production. Furthermore, the system can operate relatively insensitive to water and free fatty acid concentrations in the lipid. Consequently, a system according to the present disclosure can run without preprocessing the lipid (e.g., titrating or removing water). However, filtering of the input streams (e.g., lipid, alcohol) can be done to minimize the possibility of plugging the reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, a numbering convention is followed in which the first digit corresponds to the drawing figure number and the remaining digits identify an element or component in the drawing. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

FIG. 1 illustrates an example of a system according to the present disclosure.

FIG. 2A illustrates an example of a conduit according to the present disclosure.

FIG. 2B illustrates an example of cross section 2B of the conduit in FIG. 2A.

FIG. 2C illustrates an alternative example of the cross section 2B of the conduit in FIG. 2A.

FIG. 3 illustrates an example of a reactor according to the present disclosure.

FIG. 4 illustrates a flow chart of an example of a method according to the present disclosure.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which can be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments can be utilized and that structural, logical, and electrical changes can be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense.

FIG. 1 illustrates an example of a system 100 according to the present disclosure. System 100 includes a lipid input tank 102 and an alcohol input tank 104. Lipid input tank 102 can contain a lipid such as, but not limited to: a fat, a wax, a sterol, a fat soluble vitamin, a monoglyceride, a diglyceride, a triglyceride, a phospholipid, algae-based lipid, or combinations thereof. In an embodiment, the lipid tank 102 includes at least one of a plant oil (e.g., vegetable oil) or an animal fat (e.g., tallow). Lipids, such as more viscous lipids, can be heated within the lipid input tank 102 to improve flow. The system 100 can, for example, operate insensitive to a free-fatty acid content of the lipid. That is, the system can synthesize biodiesel from a variety of lipids with a range of free fatty acid concentrations with little to no chemical pre-processing. Further, system 100 can operate with a lipid independent of a water concentration of the lipid with little to no chemical pre-processing. The alcohol, supplied by alcohol input tank 104, can include a C1-C6 alcohol. In an embodiment, a reaction product conduit (e.g., pressure regulated reaction product conduit 136) can heat an input tank 102, 104, such as before or after separator 116.

System 100 can, in an embodiment, include a lipid input conduit 120 or an alcohol input conduit 122. A conduit can, for example, include a hollow passageway for conveyance of a fluid. In an embodiment, lipid input conduit 120 can include pump 106-1 and alcohol input conduit 122 can include pump 106-2. Pumps 106-1 or 106-2 can, for example, include, but are not limited to: a positive displacement pump, an impulse pump, a velocity pump, a gravity pump, a steam pump, or a valveless pump.

Lipid input conduit 120 and alcohol input conduit 122 can join to form a reaction mixture input conduit 124. The contents of the lipid input conduit 120 and the contents of the alcohol input conduit 122 can mix at a y-branch or at a mixing unit operation such as, but not limited to, a: ribbon blender, V-blender, cone screw blender, screw blender, double cone blender, double planetary high viscosity mixer, counter-rotating, double and triple shaft, vacuum mixer, planetary disperser, high shear rotor stator and dispersion mixer, paddle, jet mixer, mobile mixer and drum blender, or combination thereof.

Pumps 106-1 and 106-2 can regulate flow rate or pressure of a composition, such as within the reaction mixture input conduit 124. In an embodiment, the contents of the lipid input conduit 120 and the contents of the alcohol input conduit 122 can be regulated by pumps 106-1 and 106-2 such that the reaction mixture conduit 124 contains a reaction mixture with an excess of alcohol. For example, the reaction mixture can include an alcohol to lipid molar ratio in a range of from 1:1 (alcohol:lipid) to 50:1. In an embodiment, the alcohol to lipid molar ratio can include 33:1.

In an example, reaction mixture input conduit 124 can include a pump that provides the reaction mixture to a heat exchanger 108. In such an example, pumps 106-1 and 106-2 can be omitted and a low pressure metering system can be used on each conduit 120 and 122 to regulate a reaction mixture flow rate or composition of the reaction mixture in reaction mixture input conduit 124.

The heat exchanger 108 can include a first pipe (e.g., reaction mixture conduit 124) and a second pipe (e.g., reaction product conduit 132) helically intertwined about an axis A of FIG. 2B and 2C. The first and second pipes can include a first and second lumen, respectively. The heat exchanger 108 can include a conduit 201, as discussed in connection with FIG. 2A, 2B, and 2C, herein. In an example, the heat exchanger 108 can conserve thermal energy of the reaction product conduit 132. A warmed reaction mixture conduit 128 can provide warmed reaction mixture to a pre-heater 110.

Pre-heater 110 can include a heater, such as, but not limited to: an electric heater, a gas heater, a geothermal heater, a solar furnace, among others. The pre-heater 110 can heat the warmed reaction mixture of the warmed reaction mixture conduit 128 via conduction, convection, radiation, or combinations thereof. The pre-heater 110 can provide heated reaction mixture through a heated reaction mixture conduit 130 to a reactor 112.

The reactor 112 can include a sintered plug in a vessel fluidly coupled to a first pipe (e.g., heated reaction mixture conduit 130) and to a second pipe (e.g., reaction product conduit 132). The plug can include pores of at least 0.01 micrometers (μm) diameter and be configured to catalyze a reaction, such as transesterification. In an example, the reactor 112 can include a reactor heater 113. The reactor heater 113 can, regulate (e.g., maintain) reaction conditions (e.g., temperature) within the reactor 112. The sintered plug can, for example, include a sintered composite of heterogeneous catalysts, as described herein The reactor 112 can include reactor 312, as discussed in connection with FIG. 3, herein.

The reaction product conduit 132 can provide reaction product to the heat exchanger 108. In an example, the reaction product 132 can provide reaction product to a supplemental reactor in series with the reactor 112, so as to further react any unreacted reactants, such as lipids and alcohol. The supplemental reactor can be similar to the reactor 112 described herein. In various examples, multiple reactors can be arranged in parallel or in series. Reaction product can include biodiesel, as well as byproducts such as, glycerin, excess alcohol, water, or combinations thereof. Cooled reaction product can exit the heat exchanger 108 via a cooled reaction product conduit 134. Cooled reaction mixture can, be routed through a back-pressure regulator 114 to maintain a predetermined pressure between the back-pressure regulator and the pumps 106-1 and 106-2. The predetermined pressure can be based on a number of factors, such as, a pressure to maintain a condition of the reaction product (e.g., liquid state, gaseous state, supercritical state, viscosity, among others), regulate reaction conditions, regulate flow, or combinations thereof.

In an embodiment, the system 100 can operate at supercritical processing conditions. That is, the system can operate at a temperature or pressure above a critical point of the reaction mixture. For example, the super critical condition includes a pressure of about 8.3 MPa to about 35 MPa. Operating at such temperature and pressures can homogenize the reactants, such as the contents in the heated reaction mixture conduit 130, and bring the lipid and alcohol molecules into proximity. For example, a conduit, a heat exchanger, reactor, or heater, of the present invention, can operate at super critical conditions of the reaction mixture or reaction product. Energy costs of synthesizing biodiesel via supercritical reaction conditions can be similar or less than that of typical catalytic biodiesel production. The reactor 112 can convert free fatty acids to esters instead of soap, further reducing waste and post-reaction processing.

The contents of the pressure regulated reaction product conduit 136 can be at approximately atmospheric pressure and fed to a separator 116. The separator 116 can separate excess alcohol in the reaction product from the biodiesel or various byproducts. For example, the separator 116 can include a distillation unit operation to remove excess alcohol from the reaction product. Recovered excess alcohol can be recycled to the alcohol input tank 104 through an alcohol recycle conduit 138. In an example, the alcohol recycle conduit 138 can include an alcohol reclamation tank. The alcohol reclamation tank can, for example, control a rate of recycled alcohol back to the alcohol input tank 104. Biodiesel product can be feed to a biodiesel storage tank 118 via a biodiesel product conduit 140.

In an embodiment, the system 100 can be transportable. For example, the system 100 can be transported by a light motor vehicle (e.g., a vehicle smaller than a commercial semi-truck). The system 100 can, for example, be separated into a number of discrete subsections, further lending the system to transportability. Each subsection can, for example, fit through a standard doorway or stack for ease of transportability. For example, the system 100 can include an input subsection, a refinery subsection, and an output subsection. The input subsection can include the input tanks 102, 104. The refinery subsection can include the back-pressure-regulator 114, the heat exchanger 108, the pre-heater 110, the reactor heater 113, and the reactor 112. The output subsection can include the separator 116, the storage tank 118, the alcohol recycle conduit 138, and the biodiesel product conduit 140.

FIG. 2A illustrates an example of a conduit 201 within the heat exchanger 108 (FIG. 1) according to the present disclosure. The conduit 201 includes a first lumen and a second lumen, the first lumen is configured to carry a first fluid in a first direction and the second lumen is configured to carry a second fluid in a second direction, the first lumen is helically twisted relative to the second lumen, and the second lumen is configured to conductively transfer thermal energy to the first lumen for a substantial portion of a length of the conduit 201. A lumen includes a hollow passageway for conveyance of a fluid. For example, a pipe or tube can include a lumen for conveyance of a fluid. In an embodiment, the first lumen can include a first metal tube and the second lumen can include a second metal tube. For example, the first metal tube can be helically twisted relative to the second metal tube, wherein the first metal tube includes a first lumen and the second metal tube includes a second lumen.

The first lumen can include, for example, an inlet of a pumped reaction mixture conduit 224, corresponding to the reaction mixture conduit 124 of FIG. 1, and an outlet including a warmed reaction mixture conduit 228, corresponding to the warmed reaction mixture conduit 128 of FIG. 1. The second lumen can include, for example, an outlet of a cooled reaction product conduit 234, corresponding to the cooled reaction product conduit 134 of FIG. 1, and a reaction product conduit 232, corresponding to the reaction product conduit 132 of FIG. 1. In an example, the first metal tube and the second metal tube can include an internal textured surface or a textured surface layer. A textured surface, can, for example, increase thermal energy transfer between the first lumen and the second lumen. The first metal tube and the second metal tube can, for example, have a thermal interface formed by a thermally conducting filler material 244, as described herein.

The substantial portion configured to conductively transfer thermal energy can include a first segment with a first axis A and a second segment with a second axis B, where the first axis A is different than the second axis B. For example, conduit 201 can include a number of segments 242-1, 242-2, 242-3, each with a unique axis, A,B,C respectively. In an embodiment, each of the number of segments are of a continuous conduit 201. For example, a conduit 201 can be bent at two separate locations into a u-bend 246-1, 246-2 to form the three segments 242-1, 242-2, and 242-3 of FIG. 2A. The segments 242-1, 242-2, and 242-3 can increase an overall thermal contact surface area of the substantial portion without increasing a dimension (e.g., length, height, or width) of a heat exchanger (e.g., FIG. 1, 108). In an example, segments can be linked by a u-bend 246-1, 246-2.

The conduit 201 can, for example, flow countercurrent, such that the first lumen is configured to carry the first fluid in the first direction and the second lumen is configured to carry the second fluid in the second direction, wherein the first direction is different than the second direction. As shown by the arrows in FIG. 2A, the conduit 201 is configured for countercurrent flow. In one embodiment, the conduit 201 can flow parallel, wherein the first direction is the same as the second direction. Countercurrent flow transfers more heat than concurrent flow, and therefore can provide the benefit of heating the reaction mixture the greater of the two examples. Additional factors that can affect design considerations between a countercurrent and a concurrent flow heat exchanger include, but are not limited to: construction cost, space restrictions, temperature for unit operations upstream of outlets, material restrictions, twist density, lumen diameter, pressure considerations, flow rate of the reaction mixture or reaction products, and temperature of the reaction mixture or reaction products at the inlets.

FIG. 2B is an example of a cross section 203 of the conduit 201 in FIG. 2A. The cross section 203 includes a first tube 229, including a first lumen 227, and a second tube 237, including a second lumen 235. The first lumen 227 is configured to carry a first fluid in a first direction and the second lumen 235 is configured to carry a second fluid in a second direction. As show, the first lumen 227 is helically twisted relative to the second lumen 235, and the second lumen 235 is configured to conductively transfer thermal energy to the first lumen 227 for a substantial portion of a length of the conduit. It is to be understood that the lumens 227, 235 are designated using the terms first and second for ease of description, and that the terms first and second can be interchanged.

The first lumen 227 and the second lumen 235 can have a thermal interface formed by a thermally conducting filler (e.g., metallic filler) 244. The thermally conducting filler 244 can include, but is not limited to a: thermal grease, thermal gel, thermal compound, thermal paste, heat paste, heat sink paste, heat transfer compound, heat transfer paste, heat sink compound, ceramic based thermal compound, metal based thermal compound, carbon based thermal compound, liquid metal based thermal compound, or combination thereof. In an example, the thermally conducting filler 244 can include a brazing, which can, for example, join the first lumen 227 and the second lumen 235. In an example, the thermally conducting filler 244 includes a silver braze.

The thermally conducting filler 244 can, for example provide a thermal conductivity bridge between the first lumen 227 and the second lumen 235. That is, the thermally conducting filler 244 can provide a medium for thermal energy transfer between the second lumen and the first lumen.

The fluid within conduit 201 can flow in a turbulent manner. That is, the flow of the fluid in the first or second lumen can have a Reynolds (Re) number of 5000 or greater. In an example, the fluid within the conduit 201 can flow in a laminar fashion. The conduit 201 can, be contained in a thermally insulated environment to increase heat transfer efficiency. For example, an insulated heat exchanger (e.g., 108, FIG. 1) can provide an environment conducive to thermal transfer between the lumens and not an outside environment.

FIG. 2C is an example of a cross section 283 of the conduit 201 in FIG. 2A. The cross section 283 includes a first tube 289, including a first lumen 287, and a second tube 297, including a second lumen 295. The first lumen 287 is configured to carry a first fluid in a first direction and the second lumen 295 is configured to carry a second fluid in a second direction. As show, the first lumen 287 is helically twisted relative to the second lumen 295, and the second lumen 295 is configured to conductively transfer thermal energy to the first lumen 287 for a substantial portion of a length of the conduit. It is to be understood that the lumens 287, 295 are designated using the terms first and second for ease of description, and that the terms first and second can be interchanged.

The first lumen 287 and the second lumen 295 can have a thermal interface formed by a thermally conducting filler (e.g., metallic filler) 244. The thermally conducting filler 244 can include, but is not limited to a: thermal grease, thermal gel, thermal compound, thermal paste, heat paste, heat sink paste, heat transfer compound, heat transfer paste, heat sink compound, ceramic based thermal compound, metal based thermal compound, carbon based thermal compound, liquid metal based thermal compound, or combination thereof. In an example, the thermally conducting filler 244 can include a brazing, which can, for example, join the first lumen 287 and the second lumen 295. In an example, the thermally conducting filler 244 includes a silver braze. The thermally conducting filler 244 can include a filler as described herein.

As shown in FIG. 2C, the first tube 297 can have a first wall 288, wherein the first wall 288 has a first flat region 286 on an external surface 284. The second tube 289 can have a second wall 298, wherein the second wall 298 has a second flat region 296 on an external surface 294. The first flat region 286 and the second flat region 296 can be joined or coupled along one of the segments 242-1, 242-2, and 242-3. In an example, the first flat region 286 and the second flat region 296 can be joined with the thermal material 244, described herein. The coupling between the first and the second flat regions 286, 296 can, in an example, include a thermal grease, brazing, weld, solder, or other thermal bond capable of conducting thermal energy. Advantages of such an embodiment, as shown in FIG. 2C, can include increased surface area for thermal energy transfer between the fluids, lumens, and tubes of the conduit 201.

FIG. 3 illustrates an example of a reactor 312 according to the present disclosure. Reactor 312 can also illustrate an additional one or more reactor in series or parallel with reactor 112 of FIG. 1, as described herein. The reactor 312 includes a shell 358 with an input port 354 configured to receive a reaction mixture and an output port 356 configured to discharge a reaction product. The reaction mixture can include a heated reaction mixture received, for example, from a heated reaction mixture conduit 330, corresponding to heated reaction mixture conduit 130 of FIG. 1. The reaction product can, for example, discharge to a reaction product conduit 332, corresponding to reaction product conduit 132 of FIG. 1.

The shell 358 can include a material suitable to operate at reaction conditions (e.g., temperature or pressure). For example, the shell 358 can include stainless steel. In an embodiment, the reactor 312 can operate at supercritical conditions of the reaction mixture. The reactor 312 can, operate at temperatures of up to 500 degrees Celsius (° C.). In one embodiment, the reactor can operate at pressures of up to 35 megapascals (MPa).

The reactor 312 includes a sintered plug 352 within the shell 358. The sintered plug 352 includes a first catalyst, where the first catalyst is configured to transform the reaction mixture into the reaction product. The sintered plug 352 includes pores 353 of at least 0.01 micrometers (μm) diameter. In an embodiment, the reactor can include a plug with pores of at most 100 μm diameter.

In an example, a forming gas used to produce the sintered plug can include hydrogen and at least one catalyst augmentation compound. A catalyst augmentation compound can include, for example: oxygen, chlorine, nitrogen, formaldehyde, a gas-metal decomposable mix, and argon.

The sintered plug 352 can, for example be sintered in the shell 358. In an example, the sintered plug 352 can be sintered and then press fit into the shell 358. For example, the sintered plug 352 can be plastically deformed and press fit into the reactor. In either example, sintered plug 352 can be configured (e.g., bonded to the shell) so as to substantially prevent flow around the plug.

In an example the first catalyst can include any stainless steel alloy in the stainless steel family. That is a stainless steel, as is understood by one of ordinary skill, can be the material of the sintered plug. In an example, the first catalyst includes stainless steel 316L.

The sintered plug 352 can, for example, include a second catalyst, including a heterogeneous non-consumed particle. The heterogeneous non-consumed sintered particle can include, but is not limited to, an ore, zirconia, titania, or alumina. The second catalyst can, for example, be combined with the first catalyst during the sintering of the sintered plug. That is, the second catalyst, in an example, can be a sintered second catalyst.

The reactor 312 can, include a thermowell 350. The thermowell 350 can protect a sensor used to monitor reaction conditions within the reactor 312. A sensor in the reactor 312 can aid in a number of system unit operations. For example, a temperature sensor within the reactor 312 can aid in determining operating conditions of the reactor 112 or pre-heater 110. For example, the thermowell 350 can be used to gather a direct measurement of the contents of the reactor 112. In an example, a probe may include a thermowell to itself. That is, the probe can be constructed and inserted into the thermowell 350 such that the probe acts as a thermowell. Reactor 312 can include a pressure sensor.

FIG. 4 illustrates a flow chart of an example of a method 470 according to the present disclosure. A reaction mixture is provided to a heat exchanger, the reaction mixture including a lipid and an alcohol, at 472. In an example, a pump can pump the reaction mixture to the heat exchanger. The pump can, for example, push the reaction mixture so that the reaction mixture flows turbulently.

At 474, the reaction mixture is warmed in the heat exchanger, wherein the heat exchanger includes a first pipe including the reaction mixture helically intertwined about an axis with a second pipe, wherein the second pipe includes reaction products of a biodiesel reaction. The heat exchanger can operate as discussed in connection with FIGS. 1-2B, herein.

In an example, method 470 can include further heating the reaction mixture via a pre-heater. The reaction mixture can be heated to a supercritical temperature for biodiesel synthesis.

The reaction mixture is reacted in a reactor at supercritical conditions at 476. The reactor includes a sintered plug in a vessel fluidly coupled to the first pipe and to the second pipe, the plug having pores of at least 0.01 micrometers (μm) diameter and the plug configured to catalyze a reaction. The reactor can include a reactor heater 113, a thermowell 350, a sintered plug 352, one or more pores 353, or shell 358 as discussed in connection with FIGS. 1 and 3, as discussed herein.

In an example, method 470 can include separating excess alcohol from biodiesel products and recycle the separated excess alcohol to an alcohol input tank.

The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 

What is claimed is:
 1. A system, comprising: a heat exchanger including a first lumen and a second lumen helically intertwined about an axis; and a reactor including a sintered plug in a vessel in fluid communication with the first pipe and the second pipe, the plug having pores of at least 0.01 micrometers (μm) diameter and the plug configured to catalyze a reaction.
 2. The system of claim 1, wherein the reactor is configured to operate at a temperature of up to 500 degrees Celsius (° C.).
 3. The system of claim 1, wherein the reactor is configured to operate at a pressure of at least 8.3 megapascals (MPa).
 4. The system of claim 1, including a heater is in fluid communication with the first pipe and configured to add thermal energy to the system.
 5. The system of claim 1, wherein the system is configured to be transportable.
 6. The system of claim 1, wherein the sintered plug includes stainless steel.
 7. A conduit, comprising a first lumen and a second lumen, the first lumen configured to carry a first fluid in a first direction and the second lumen configured to carry a second fluid in a second direction, the first lumen is helically twisted relative to the second lumen, and the second lumen configured to conductively transfer thermal energy to the first lumen for a substantial portion of a length of the conduit.
 8. The conduit of claim 7, wherein the first lumen includes a first metal tube and the second lumen includes a second metal tube.
 9. The conduit of claim 8, wherein the first metal tube and the second metal tube have a thermal interface formed by a thermally conducting filler material.
 10. The conduit of claim 7, wherein the first metal tube has a first wall, the first wall having a first flat region on an external surface, and the second metal tube has a second wall, the second wall having a second flat region on an external surface, the first flat region and the second flat region joined along the substantial portion.
 11. The conduit of claim 7, wherein the first direction is different than the second direction.
 12. The conduit of claim 7, wherein the substantial portion has a first segment with a first axis and a second segment with a second axis, the first axis different than the second axis.
 13. A reactor, comprising: a shell having an input port configured to receive a reaction mixture and an output port configured to discharge a reaction product; and a sintered plug within the shell, the sintered plug having a first catalyst, the first catalyst configured to transform the reaction mixture into the reaction product, the plug having pores of at least 0.01 micrometers (μm) diameter.
 14. The reactor of claim 13, wherein the first catalyst includes stainless steel.
 15. The reactor of claim 13, wherein the reaction mixture includes an alcohol and a lipid.
 16. The reactor of claim 15, wherein the alcohol includes a C1-C6 alcohol.
 17. The reactor of claim 15, wherein the lipid includes at least one of a plant oil or an animal fat.
 18. The reactor of claim 13, wherein the sintered plug has pores of at most 100 μm diameter.
 19. The reactor of claim 13, wherein the sintered plug includes a second catalyst, including a heterogeneous non-consumed particle.
 20. The reactor of claim 19, wherein the second catalyst includes at least one of sintered ore, sintered zirconia, sintered titania, and sintered alumina.
 21. A method for biodiesel production, comprising: providing a reaction mixture to a heat exchanger, the reaction mixture including a lipid and an alcohol; pre-heating the reaction mixture in the heat exchanger, wherein the heat exchanger includes a first pipe including the reaction mixture, the first pipe helically intertwined about an axis with a second pipe, wherein the second pipe includes a reaction product of a biodiesel reaction; and reacting the reaction mixture in a reactor a supercritical condition to produce the reaction product, wherein the reactor includes a sintered plug in a vessel fluidly coupled to the first pipe and to the second pipe, the plug having pores of at least 0.01 micrometers (μm) diameter and the plug configured to catalyze a reaction.
 22. The method of claim 21, wherein reacting the reaction mixture comprises the biodiesel reaction of transesterification and esterification.
 23. The method of claim 21, wherein the super critical condition includes a pressure of about 8.3 MPa to about 35 MPa.
 24. The method of claim 21, wherein the reaction mixture includes an excess of alcohol to lipid.
 25. The method of claim 21, wherein the lipid includes a free fatty acid concentration of up to about 60 wt %.
 26. The method of claim 21, wherein the lipid includes a water concentration of up to about 10 wt %.
 27. The method of claim 21, including: recovering excess alcohol from the reaction product; and recycling the recovered excess alcohol to an alcohol input tank or an alcohol reclamation tank.
 28. The method of claim 21, including reacting the reaction product, after reacting the reaction mixture, in a supplemental reactor in series with the reactor. 